OPC UA is a known standard protocol for manufacturer-independent communication, in particular in process automation, specified by the OPC Foundation. Although the original name for OPC was OLE for Process Control, OPC has been used without an indication of an abbreviation. UA stands for Unified Architecture.
FIG. 1 and FIG. 2 illustrate known arrangements for interaction according to the OPC UA specification. In this case, FIG. 1 shows an OPC UA client 1 which can interact with an OPC UA server 3 by OPC UA service calls using the OPC UA protocol and a communication system 2. However, an OPC UA server can also act as a client with respect to other servers and can compile the data from the latter and provide the data to clients in its address space. FIG. 2 illustrates such an arrangement. An OPC UA client 1 interacts with a server, which can be called the aggregating OPC UA server 4, which in turn can communicate with two OPC UA servers 3 via the communication system 2.
Client/server operation according to the OPC UA standard can be used in many fields, for example, in production management systems or in production planning, and generally in control engineering. Client and server functions can be implemented, for example, in devices and controllers. In such arrangements, OPC UA can make it possible not only to read and write data but also to change organizational structures for data. As a result, OPC UA clients are able to tackle both complex configuration tasks and engineering tasks or other tasks which write data and/or involve structural changes. Whether an OPC UA client has to make either all changes or no changes to a plurality of OPC UA service calls can depend on such tasks. This is relevant if a plurality of OPC UA clients simultaneously make changes to an OPC UA server. Database systems are known which use transactions. However, a transaction context has hitherto not been specified for OPC UA. The granularity of data manipulation actions can involve a plurality of OPC UA service calls but a transaction context has not been specified for an individual OPC UA service call. The case in which individual write operations are successful and others are not may even occur in the case of an individual OPC UA service call which involve, for example, writing to a plurality of values.